1. Technical Field
The present invention relates to liquid discharge apparatuses, methods for controlling the liquid discharge apparatus, and programs for controlling the liquid discharge apparatus and, in particular, relates to a liquid discharge apparatus having a plurality of independently detachable print head units, a method for controlling the liquid discharge apparatus, and a program for controlling the liquid discharge apparatus.
2. Related Art
Printing apparatuses, such as an ink jet printer, eject ink from nozzles to print. If a failure, e.g., clogging of any nozzle in a print head, occurs during printing, the typical printing apparatus detects the failure and issues an alarm or cleans the nozzles to eliminate the failure. In some cases, however, the failure is not eliminated by cleaning.
According to a known technique, a spare print head is provided for the printing apparatus in order to more reliably eliminate such a failure in the print head. Upon occurrence of a failure, the print head is replaced with the spare head. Alternatively, ink is discharged from nozzles of the spare print head instead of those of the print head in which clogging is detected. For example, JP-A-2003-118149 discloses this technique.
In the case where the printing apparatus includes the spare print head, as long as the print head, serving as a main print head, is replaced with the spare one upon occurrence of a failure in the main print head, the spare print head is not used until the end of the life of the main print head. Alternatively, as long as the nozzles of the spare print head are used only upon occurrence of a failure in the nozzles of the main print head, the main print head predominantly prints. In either case, the nozzles of the spare print head are not used unless a failure occurs. However, the lower frequency of use of the print head leads to drying of ink which remains in the nozzles of the print head. Unfortunately, the interiors of the nozzles may be caked with the remaining ink, causing the clogging of ink. Alternatively, ink particles may accumulate in the interiors of the nozzles, so that it is difficult to discharge ink from the nozzles.